This invention relates to a fuel-injection nozzle adapted for use with a diesel engine and, more particularly, to a pin-type fuel-injection nozzle.
The rate at which a fuel is injected into the combustion chamber of a diesel engine is controlled as indicated in FIG. 1. The fuel injection rate is so controlled that, although it is initially low, it rises substantially at the termination of the injection period. Thus, an attempt is made to minimize the effects of diesel knocking and the accompanying noises. Therefore, the diesel engine involves a pin-type fuel-injection nozzle which is capable of allowing for the fuel-injection characteristic illustrated in FIG. 1. However, the above-mentioned pin-type fuel-injection nozzle has certain drawbacks, in that carbon particles are deposited on the inner peripheral wall of the injection hole and the outer peripheral wall of the nozzle needle pin, tending to stop up the surrounding annular gap which is defined between the inner peripheral wall of the injection hole and the outer peripheral wall of the nozzle needle pin, and failing to stabilize the characteristic of the fuel injection rate shown in FIG. 1, for periods which run into hours.
The choke pin nozzle disclosed in U.S. Pat. No. 4,375,274 is intended to prevent the plugging of the above-mentioned annular gap resulting from the deposition of carbon particles. This known choke pin nozzle involves a nozzle needle which is rotatable around the axis of the choke pin nozzle during its operation. The nozzle needle of the published choke pin nozzle entails a choke pin which is offset from the axis of the injection hole. Therefore, the proposed choke pin nozzle, which is constructed as described above, has certain advantages, in that the rotation of the choke pin, in conjunction with the nozzle needle during operation, allows for the flushing out of carbon particles deposited on the outer peripheral wall of the choke pin and the inner peripheral wall of the injection hole, thereby suppressing the plugging of the annular gap defined between the inner peripheral wall of the injection hole and the outer peripheral wall of the choke pin.
According to the choke pin nozzle set forth in the U.S. Pat. No. 4,375,274, the choke pin is offset from the axis of the injection hole, thereby forming a single broader section on one half of the annular gap. It is intended to prevent carbon particles from depositing in the walls which define the broader gap section by the force of a fuel flowing along the broader gap section. However, the published fuel injection nozzle constructed as described above has the drawbacks that the aforementioned broader gap section unavoidably has a large open area; fuel is injected through the broader gap section in the form of coarse particles, thereby failing to be sufficiently atomized; and fuel is unevenly distributed, presenting difficulties in effectively reducing knock noises.